Kamigawa block (2004) Besides the first appearance of a gold card in the updated frame, Kamigawa block also created the flip cards, that would have different rules for each side
For instance, in early 2021 this card sold for an impressive $110,100
Amass branches off into enough different strategies (aristocrats, tokens, +1/+1 counters, zombies matter) that its just an altogether good mechanic
RNGesus blesses us with a win but we get no booster packs
Distributed to moviegoers at Pokmon the Movie 2000, it features runic text and a unique card back never used again in the TCG
In one example, a Pokmon Base Set collection including a Charizard graded PSA 8 carried a pre-auction estimate of 300-500 and sold for 675 including premiums, whereas the same card ungraded would be in the region of 150-250 for similar condition